Molten metal applicators for glass filaments



Sept. 26, 1961 H. B. WHITEHURST ET AL 3,001,507

MOLTEN METAL APPLICATORS FOR GLASS FILAMENTS Filed Aug. 4, 1954 Big-.4.

HAEEYB- WHITEHURST 6: WILLIAM H. 0710 IN VEN TORS A TTOENE Y5 3,001,507MOLTEN NIETAL APPLICATORS FOR GLASS FILAMENTS Harry B. Whitehurst andWilliam H. Gtto, Newark, Ohio,

assignors to Givens-Corning Fiberglas Corporation, a

corporation of Delaware Filed Aug. 4, 1954, Ser. No. 447,864- 7 Claims.(Cl. 118-401) This invention relates to metal coating of filaments orfibers, and more particularly to molten metal applicators for applyingmetal coatings to continuous glass filaments.

This application is a continuation-in-part of applications, SerialNumber 319,724, filed on November 10, 1952, now Patent 2,772,518, andSerial Number 322,598, filed on November 26, 1952, now US. Patent No.2,963,- 739, both filed in the names of the present inventors.

It is well known that glass filaments have extremely high strengthcharacteristics as well as highly desirable flexing characteristicswhich make them of particular advantage 'for many uses and applicationsas reinforcing agents. Such fibers, however, have a weakness to surfaceabrasion which reduces their overall ability to withstand wear to theextent that it eliminates the possibility of their application for manyuses in which the strength and flexibility of the filaments would behighly desirable. The coating of glass filaments with metal such ascopper, zinc, aluminum, silver or alloys thereof, it has been found, ishighly successful in providing protection against abrasion. Difiicultyhas been experienced, however, in applying the metal to such filamentsat a high rate of speed and with uniformity so as to make iteconomically feasible to produce them in mass production.

As set out in the above metnioned copending applications, production ofmetal-coated glass filaments can be accomplished by passing the bareglass filaments through beads or globules of molten metal and coating bywetting each filament, to form a layer of the metal integrallyassociated with the glass filaments.

In the present instance it is a principal object of the invention toprovide a new applicator means for applying metal to glass filamentswhich permits economical production of coated filaments at a high rateof speed, while at the same time providing uniformity without the needfor great care and attention.

A further object of the invention is to provide applicator means forapplying metal to glass filaments on a continuous basis controllable toprovide a predetermined linear and peripheral uniformity of coating.

Another object of the invention is to provide applicator means forapplying metal on glass filaments without disrupting or deleteriouslyaffecting the desired physical characteristics of the filaments.

Still another object of the invention is to provide an efiicient andeconomical applicator means for applying metal to glass filaments whichreadily lends itself to being adapted to conventional filament-formingmeans.

The application of metal to glass filaments in accordance with the aboveobjects is accomplished in the present instance by pulling or drawingthe filaments through an accumulation of molten metal such as a globuleor bead of such metal. In particular, the apparatus is arranged so as topermit drawing of filaments through such metal in vertical paths whichfacilitates adapting such coating operations to conventionalfilament-forming means.

To accomplish this result, it has been found that a quantity of moltenmetal maybe suspended without undersupport by allowing it to projectfrom an orifice in a substantially vertical applicator face, thusproviding an unobstructed path above and below such metal for freeassage of fi aments through the metal- .BY making the orifice small,such as a thin slot, the molten metal supplied thereto can projectoutwardly and overhang the edge of the slot to envelop the filaments atthe applicator face without freely flowing because of the restriction toflow offered by the surface tension of the metal or its oxide. With asmall orifice, the quantity of metal projecting therefrom can also bemade independent of changes in pressure of the fluid over a range ofheads within the limits of size of the container portion holding themolten metal.

A feature of the invention is that it permits the application of metalcoatings to glass fibers at a very rapid rate.

Another feature lies in the fact that this invention is readily adaptedto permitting application of metal coatings to glass filaments duringtheir forming: process.

Still another feature of the invention lies in the fact that metal maybe controllably fed from a common source of supply to a multiplicity offilaments simultaneously with but a limited amount of care beingrequired to effect the desired degree of coating.

A further feature of the invention is that the care and attention tooperation required to produce metal-coated filaments in mass productionare reduced to the extent that a greater degree of concentration may bedirected' to other factors of quality control.

Other objects and features which we believe to be characteristic of ourinvention are set forth with particularity in the appended claims. Ourinvention, however, both in organization and manner of constructiontogether with further objects and advantages thereof may be bestunderstood by reference to the following description talllcler;1 inconnection with the accompanying drawings in w c FIGURE 1 is a partlybroken away side-elevational view in cross section of a metal applicatorcomprising an embodiment of the present invention;

FIGURE 2 is a front-elevational view in part of the metal applicator ofthe invention shown in FIGURE 1 in which grooves are provided in theslotted applicator ace;

FIGURE 3 is a cross-sectional side elevational view of a portion ofanother metal applicator unit in which the metal outlet portion isupwardly inclined;

FIGURE 4 is an enlarged View of the face of the metal applicator unit ofFIGURE 3 showing the closely spaced filament grooves incorporatedtherein;

FIGURE 5 is a view of the face of the applicator unit of FIGURE 4 astaken on line 5-5; and

FIGURE 6 is a cross sectional perspective view of another metalapplicator unit embodying the principles of the present invention.

Turning to the drawings in greater detail, FIGURES l and 2 show aslotted applicator 48 having vertical grooves 56 disposed in the face 53to accommodate the filaments passed over the face to permit them to passthrough the base of the longitudinal globule 55 emitted from the slot54. The slot 54 extends across the width of the face and has the grooves56 cutting thereacross at right angles. In this arrangement the slotportions between grooves 56 otier a partial and augmenting support forthe longitudinal globule 55 in such cases where the temperatures of themetal are so high as to provide a limited amount of surface tension forsupport of the globules. The struc ture made in this manner, providesunobstructed filament paths over the face 53 through the grooves 56 andadditionally eliminates the need for projection of the globule beyondthe extremities of the face 53 in view of the fact that on passagethrough the grooves the filaments will pass through. the metal emergingfrom the slot.

In the applicators made in accordance with the present Patented Sept.26, i

invention, the material contacted by the molten metal contained andsupplied to the filaments is preferably of a type which is non-wettableby the molten metal. In particular, it is preferable that the face andchannel or passage from which the metal is emitted be of material suchas carbon or graphite which, in general, is not wet table by metal. Withsuch an arrangement, the metal emitted fro-m the orifice will not tendto clog in the channel nor flowingly spread over the face, but rather,will assume a configuration determined by the shape of the orifice fromwhich it is emitted. The accumulation of metal thus emerging from theorifice additionally can be made to assure a globular form projectingbeyond the applicator orifice boundaries.

A filament being formed can be passed through such a globule withoutdisplacing the globule from its position at the end of the passage, andas the filament passes through the globule, a coating of metal isimparted thereto. In the case of oxidizable metals, a film of oxide mayform over the globule supported at the orifice which, in efi'ect, formsa shell with the filament passing into and out of the shell and pickingup metal while in the shell. As the metal is removed from the inside ofthe shell, additional metal flows into the shell to replace the metalthat has been taken out by the coated filament.

In the use of materials such as carbon and graphite which generally willnot become wet out by molten metals, it has been found that while themetals will not readily wet out over the surface of the material, themetal may be swaged or worked into solid clinging relationship with thenon-wettable material such as with a wire brush to promote formation ofan oxide film of the metal over predetermined areas of the face overwhich the fresh molten metal will readily flow. This property can beadvantageously utilized in operation of applicator units of the presentinvention to cause globular accumulations of metal of most desirableconfiguration for fiber envelopment to be projected from the face of theapplicator.

FIGURES 3, 4 and 5 show a metal applicator in which these properties arefurther utilized to advantage. Metal 60 contained within the applicatorunit is fed to the face 68 through an upwardly sloping channel 62 toform a globular accumulation of molten metal 61 projecting from the facefor envelopment of filaments 63 passed therethrough. The interior 64 ofthe container portion of the applicator unit is made of heat-resistantmaterials capable of withstanding the temperatures of the molten metalcontained, While the exterior may be a different refractory material 66,if desired. Between the interior and exterior materials of the unit,heater elements 67 are embedded within a high temperature material andprovide the heat for melting and retaining the metal 60 in moltencondition.

The face '68 of the applicator unit is constructed so that the orificeat the end of channel '62 is bounded by material such as graphite whichis relatively non-wettable by molten metal. Thus, on emergence from theorifice, the metal 61 will not of itself tend to cling to the boundariesof the orifice, but rather will remain self-contained and supported byits own surface tension. If desired, however, the edges of the orificemay be swaged to provide an oxide film within desired boundaries of theorifice edge over which the molten metal may flow to form a slightlylarger globule and a clinging relationship of the molten metal to theorifice edges. The channel 62 is also preferably of non-wettablematerial so that tendencies toward formation and collection of oxidewithin the channel are minimized to the extent that difficulty fromclogging by oxide dormations is eliminated.

Experience with applicator units of this type indicates that the metalin the channel 62 is raised in the channel 62 to the level of theglobule 61 by suction action which minimizes the dependence of metalemission from the orifice on the head of -the metal '60 in the containerportion of the unit. While not fully understood, the suction orsiphon-like action which causes the metal to be brought to the level ofthe globule 61 has been shown to be directly associated with the motionof the filament through the globule. In observing the dynamic actionclosely, it is seen that as the filaments pass through the globularaccumulation, the wetting and coating of the glass surfaces causes aremoval of metal from the globule which, it is postulated, forms a lowpressure space Within the globule and which is automatically replenishedby molten metal drawn up through the channel 62 because of the lowpressure condition. Removal of the molten metal from the globule appearsto be caused by affinity of the metal for glass as well as by theinterfacial friction between the moving filament and the metal throughwhich it passes. The coating and replenishment of metal in the globule61 also appears to be associated with the thermodynamic relationship ofthe molten metal in the globule and the hot filament passedtherethrough. In this respect, the gradual change in temperature of themolten metal on emergence from the orifice seems to cause a greateradhesion of the metal to the glass by reason of greater viscosity.

Although the pressure head of meal according to the present invention ismade to be less of a factor affecting stability of the globule, it hasbeen found that for any given set of dynamic conditions of operation ofthe unit in applying metal to the moving filaments, the pressure head ofthe metal in the reservoir portion of the applicator can be utilized todetermine or regulate the rate at which the metal flows to the globularaccumulation. A wide range of heads may be utilized to control thethickness of metal applied and may range from a positive head for thickcoatings to a negative :head for thin coatings substantially withoutaffect on the stability and effectiveness of the globule to provide theuniformity of coating desired. In many instances it has been founddesirable to operate with a negative pressure head to produce thincoatings. Under such circumstances, coating operations are firstinitiated by application of a positive pressure to get the molten metalto the orifice and then to reduce the pressure to that for the desiredcoating after the operation is started.

FIGURES 4 and 5 show ingreater detail the recesses or grooves 76 in theface 78 within which the filaments are guided and coated. The groovesare made wide enough to accommodate filaments 73 to pass therethroughbut narrow enough that the metal emitted from the slot orifice 72 ispermitted to project from the orifice and, establish a bridgingrelationship under its own surface tension between the faces of thegroove spacing projections 79. The width of the projections 79 is madesufficiently narrow that a maximum number of grooves may be formed inthe face 78, but are made wide enough that a swaging of the face of theprojections may be effected so that an oxide will form on the face ofthe separator portions to which the metal emitted from the slot orificemay cling. The metal is thus made to cling in bridging relationshipbetween the faces of the projections 79 and to fill in the space of thegrooves on emergence from the slot orifice. The metal emitted from thechannel 62 is thereby caused to reach out to the front of theprojections 79 and be retained in a stable condition over a still Widerrange of pressure heads exerted by the fluid in the container portion ofthe applicator.

The metal oxide on the face of the projections 79 in providing theclinging area for the molten accumulation, keeps the metal from fallingback down the channel leading to the slot orifice 72. Metal oxide whichcan be made to form by swaging molten metal into the grooves at thepoints of emergence from the slot orifice is also an advantage inproviding a filmto cover the graphite over which the glass filamentsride. It has been found that although graphite is a material which has alow abrasion or Wear action on glass filaments, an oxide of the metal tobe coated on the filaments will act as a base klt).

over which the molten metal can flow to permit the fluid metal to act asa lubricant for the glass filaments and thus further reduce the abrasiveaction on the filaments. The low abrasion material such as graphite,however, is still preferred as a backing material regardless of thelower abrasiveness possible with the presence of the oxide of the metal,because of conditions which might arise where the molten metal layerwould break down and the glass filaments caused to make direct contactwith the face of the applicator.

FIGURE 6 illustrates the principles of operation of another form ofapplicator unit in which the molten metal 80 heated by electrical heaterelements 87 is supplied through a wide channel 82 which diminishes insize to the limits of a narrow slot orifice in the face 88 of the unit.The channel 82 slopes upwardly to the orifice which is located so thatthe globular accumulation 81 projected therefrom is conveniently locatedfor passage of filaments therethrough.

The interior of the channel 82 is lined with diflicult-towet ornon-wettable material such as the graphite of the previous embodiments,while the interior 84 of the container portion of the applicator unitmay be of refractory or other heat-resistant material capable ofmechanically withstanding the temperature of the molten metal. Theexterior 86 may be still another suitable refractory material, ifdesired. By aligning the interior of the channel 82 with non-wettablematerial, the formation of oxide on the interior surface is minimized,and by making the bottom portion of the channel wider, a clogging withinthe longitudinal portion thereof is made practically impossible.

The wide channel is provided Without acting as a deterrent to thesuction action effected by the filament motion through the globularaccumulation 81 by reason of the fact that the hydrostatic relationshipto draw the metal through the channel is primarily established at theslot orifice of narrow dimension. The space between the front verticalwall of the container portion of the applicator and the upwardly slopingupper portion of the chanel 82 is filled in with heating-conductiverefractory material 89 to further enhance the eificiency of thermalconditions established in the unit. The heat, rather than beingdissipated from the exterior of the vertical wall above the channel 82,thus is instead transferred and retained within the unit by minimizingthe exposed surface area of the unit. Heat transfer from the body of themetal is retained in the container portion to maintain the upper portionof the channel 82 at a higher temperature so that the molten metal as itpasses through the channel 82 is maintained in a more fluid conditionthan if the upper portion of the channel were more freely exposed fordissipation of heat.

As an example of the increase in elficiency of heating the molten metalwithin the channel 82, zinc which was originally required to be raisedto a temperature of about 975 F. within the container portion of theapplicator unit for a bead or globule 81 at 820 F., in the instantembodiment need only be heated to a value of about 920 F. to provide aglobule of molten metal at the same temperature.

Although the apparatus and method herein shown and described areillustrated in connection with collection of coated filaments in strandform, it will be readily recognized that the nature of the invention issuch that the filaments may also be collected individually forapplications where conditions dictate the need for single metal coatedfilaments.

Various metals and alloys of metal may be applied to the glass fibersaccording to the present invention. Metals such as aluminum antimony,cadmium, cobalt, chromium, copper, nickel, silver, tin or alloys may beapplied. In the latter respect alloys such as zinc-titanium, lead-zinc,tinlead, brass, bronze and others can also be applied.

Different kinds of glasses may be employed to form the filaments, forinstance, calcium borosilicate glasses. Also glasses of selectedcomposition may be used to facilitate the coating and adherence of themetal to the glass filament surface. A suitable glass may contain:

Percent SiO 45.0-65.0 A1 0 4.0l7.0 B 0 2.0-1.3.0 CaO 3.0-l8.0 Na O0.2-15.0

and including from 4 to 15% by weight of an oxide of a metal from thegroup including copper, zinc, lead, tin, aluminum, silver and titanium.

glass filaments will vary with the kind of metal being used. However, byadjusting the point at which the applicator for the metal contacts thefilament being formed, it is possible to regulate the relation of thetemperatures of the cooling glass filament and molten metal at the pointat which they come intocontact.

Modifications in operation, such as operation of the applicator unitswith their faces in the vicinity of a synthesized atmosphere, may alsobe effected to produce optimum coating properties. For example, it hasbeen found that operation of the units with the points of application ina synthesized atmosphere of somewhat less than 20% oxygen but notcompletely devoid of oxygen produces coatings of high quality anduniformity.

Metal coated glass in the form of fibers, strands, yarns and the likeproduced by the apparatus of the invention may be used in many productsincluding the following:

decorative fabrics, tapes, fishing lines, awnings, uphol stery material,roofs, reinforced resins, movie screens, clothing, clutch facings;reinforcing cords for rubber products including tires, garden hose, firehose, conveyor belts, blankets, fan belts, motor belts, erasers, rugpadding, gloves; oxidizable material in flash bulbs; conductors forelectrical circuits in radio, television and other electronic equipment;radiation shields, protective wrap pings in the form of foil or fabric,laminated products comprising thin foils of glass and metal, heatingelements, resinous table tops and the like; reinforcement of metalproducts and carbon products such as motor brushes, and many more.

While We have shown certain particular fonns of our invention, it willbe understood that we do not wish to be limited thereto since manymodifications may be made within the concept of the invention, and we,therefore, contemplate by the appended claims to cover all suchmodifications which fall within the true spirit and scope of ourinvention.

We claim:

1. An applicator for coating glass fibers or the like with metalcomprising a generally vertical surface forming a face across whichfibers to be coated are drawn, said face having an orifice comprising alongitudinal slot from which molten metal is supplied in horizontallyprojecting relation for coating of fibers drawn across said face, asupply channel leading to said orifice through which said molten metalis fed, said supply channel being inclined upwardly toward said orifice,said channel having interior surfaces of material substantiallynon-wettable by said metal whereby tendencies for compounds of saidmetal to form on said surfaces are reduced.

2. An applicator for coating glass fibers or the like with metalcomprising a generally vertical surface forming a face across whichfibers to be coated are drawn, said face having an orifice from whichmolten metal is supplied for coating of fibers, a supply channel leadingto said orifice through which said molten metal is fed having interiorsurfaces of material substantially non- Wettable by said metal, saidsupply channel being inclined upwardly toward said orifice, said supplychannel having a larger cross-sectional area than said orifice at adistance along its length away from said orifice and graduallydiminishing in cross-sectional area on approach toward said orifice to asize such that the surface tension of molten metal issuing from saidorifice is of magnitude sufficient to block the free flow of metal fromsaid face but permits the metal to assume a projected globular form tocause envelopment of the fiber portions drawn across said face.

3. An applicator for coating glass fibers or the like with metalcomprising a surface forming a face across which fibers are drawn for acoating, said face having a longitudinal slot therein from which moltenmetal is supplied for coating the fibers, said slot having asufficiently small dimension transverse to its longitudinal dimensionsuch that the fluid coating material issuing therefrom is blocked fromfreely flowing from said face by its own surface tension, said facehaving fiber-accommodating grooves therein having a generallyright-angular orientation with respect to said slot, said slot andgrooves being bounded and defined by material which is substantiallynon-wettable by said metal.

4. An applicator for coating glass fibers or the like with metalcomprising a surface forming a face across which fibers are drawn for acoating, said face having a. longitudinal slot therein from which moltenmetal is supplied for coating the fibers, said face havingfiber-accommodating grooves generally oriented at right angles to saidslot, the projecting portions of said face between adjacent groovesbeing surfaced with material which is substantially Wettable by saidmolten metal, whereby said molten metal is retained in said groovesinfluenced by establishment of a clinging relation with said projectualfibers passed therethrough, the projecting portions of said face betweenadjacent grooves being surfaced with material which is substantiallywettable by said molten metal, said grooves being sufiiciently narrowthat molten metal emitted from said slot will bridge the individualgrooves in clinging relation with said projecting portions of said face,whereby fiber portions residing in said grooves on passage therethroughare fully enveloped by said molten metal to impart a coating to thefibers.

6. An applicator for coating glass fibers or the like with moltenmaterial comprising a reservoir portion for material in moltencondition, a surface providing a fibercoating face across which fibersto be coated are drawn, said face having an orifice from which themolten material is supplied for coating of fibers, a supply channelextending between said reservoir portion and said orifice, said supplychannel being inclined in generally acute angular relationship from aside of said reservoir portion to said orifice, the portion of saidapplicator within the acute angle defined by the side of said reservoirportion and said supply channed being composed of solid matter conduciveto conductive transfer of heat to-said channel, whereby the heat of themolten material contained in said reservoir aids in maintaining a hightemperature'of material passed through said supply channel.

7. An applicator for coating glass fibers or the like with metalcomprising a reservoir portion for metal in molten condition, agenerally vertical surface providing a fiber-coating face across whichfibers are drawn for a coating, said face having an orifice from whichthe molten metal is supplied for coating of fibers, a supply channelextending between said reservoir portion and said orifice, said supplychannel being inclined in generally acute angular relationship from aside of said reservoir portion to said orificeand having interiorsurfaces of material substantially non-wettable by said metal, theportion of said applicator within the acute angle defined by the side ofsaid reservoir portiontand said supply channel being composed of solidmatter conducive to conductive transfer of heat to said channel, theinlet portion of said supply channel at the end nearest said reservoirportion being generally greater in cross-sectional area than saidorifice, saidchannel diminishing in crosssectional area on approach tosaidorifice to a size such that the surface tension of molten metalissuing from said orifice is of magnitude sufficient to block the freeflow of metal from said face but permits the metal to assume a projectedglobular form to cause envelopment of the fiber portions drawn acrosssaid face,

References Cited in the file of this patent UNITED STATES PATENTS1,318,971 Heine Oct. 14, 1919 1,496,309 Girvin June 3, 1924 1,934,796Friederich Nov. 14, 1933 2,162,980 Smith June 20, 1939 2,373,078 KleistApr. 3, 1945 2,598,908 Grimson Jan. 3, 1952 2,693,429 Radtke et al. Nov.2, 1954 2,934,458 Budd et al Apr. 26, 1960 FOREIGN PATENTS 840,209France Jan. 11, 1939

